A stacking apparatus can comprise a horizontal vacuum conveyor whose feed path ends above a stacking location, a brake device below the feed path upstream of the stacking location including a vacuum chamber around which an air permeable feed member is circulated and a deflection device for deflecting the ends of the sheets from the vacuum conveyor to the brake device.
In numerous manufacturing processes, e.g. in the manufacture of impregnated paper sheets for covering plates or in the manufacture of plastic foil, it is necessary to continuously and precisely stack large sheets having an inherently unstable form at a high speed.
Since the sheets because of their instability may not be pushed over each other, a vacuum conveyor can be used on which the sheets can be conveyed suspended by the vacuum and from which they can be ejected by interrupting the vacuum. The required braking of the sheets upstream of the stacking location is effected by a brake device which engages the sheet ends. This brake device feeds sheets with considerably less speed than the vacuum conveyor. The sheet ends are pressed by a deflection device from the vacuum conveyor to the brake device.
This apparatus is described in German Printed patent application DE-OS No. 23 48 320. The vacuum conveyor comprises vacuum conveyor rollers or belts spaced from each other and extending along the feed path.
The intervening spaces are bridged by suspension strips with blower nozzles so that the sheets on this path are conveyed floating. A vacuum brake roller under the conveyor plane is spaced upstream from the stacking location.
The entering sheet ends are pressed against the vacuum braking roller with a deflection device comprising several cams or lifting members mounted on a common shaft. The last vacuum conveyor roller in the feed direction is mounted at the beginning of the stacking location. Its vacuum is periodically switched off so that the release of the sheet ends is improved. The sheets leaving the vacuum brake roller have a residual speed so that they slide until impacting on a stop.
A very large number of sheets may be be deposited with this apparatus but only at a limited speed. Large sheets (typical dimensions: 1500 to 6000 mm length, 500-4000 mm width) begin to sail and float at speeds of from about 150 m/Min. as they are conveyed in a suspended form on the conveyor and in the depositing device so that an edgewise exact stacking is no longer possible.